Peter Thorn is a Colonel in the Unites States Rangers.
A member of Delta Force and an expert in anti-terrorist activity, he is on the front line in the growing war with radicalism. He is in his mid 30's, having served 14 years in the service prior to the first book.
As the series begins, he is completing a two-year stint as leader of one of the three Delta Force detachments, a position he has enjoyed immensely and which he is giving up reluctantly. Orders are orders, though, and this career soldier knows he has no choice but to take the next rung up the ladder.
And thus he is moved to a newly created secret liaison team specializing in monitoring potential terrorist threats to not only the safety of the nation but also geared towards which could hamper the military's ability to react.
Thorn has considerable experience with the Middle East. His father was a senior officer in the Special Forces stationed for many years in that region and taking his family with him. This included three years in Iran as his father helped train the Shah's elite soldiers. This time in the region has given him more than just a solid talent in their languages; it has made him an expert in what make so many of them tick and how they are likely to react to different provocations.
A graduate of West Point, Thorn had wanted for many years to become a Ranger. Though his father had been a Green Beret and Thorn had the utmost respect for that force, the work done by the Rangers was what interested him. He saw during the incredibly rigorous training that the skills and discipline his father had instilled in him kept him going and enduring.
Now in his new job with so much depending on his ability to survive in a war where the enemy wore no uniform and fought by no rules, his training is coming in very good use.